A former employee for the National Security Agency pleaded guilty on Friday to taking classified data to his home computer in Maryland. According to published reports, U.S. intelligence officials believe the data was then stolen from his computer by hackers working for the Russian government.

Nghia Hoang Pho, 67, of Ellicott City, Maryland, pleaded guilty today to “willful retention of national defense information.” The U.S. Justice Department says that beginning in April 2006 Pho was employed as a developer for the NSA’s Tailored Access Operations (TAO) unit, which develops specialized hacking tools to gather intelligence data from foreign targets and information systems.

According to Pho’s plea agreement, between 2010 and March 2015 he removed and retained highly sensitive classified “documents and writings that contained national defense information, including information classified as Top Secret.”

Pho is the third NSA worker to be charged in the past two years with mishandling classified data. His plea is the latest — and perhaps final — chapter in the NSA’s hunt for those responsible for leaking NSA hacking tools that have been published online over the past year by a shadowy group calling itself The Shadow Brokers.

Neither the government’s press release about the plea nor the complaint against Pho mention what happened to the classified documents after he took them home. But a report in The New York Times cites government officials speaking on condition of anonymity saying that Pho had installed on his home computer antivirus software made by a Russian security firm Kaspersky Lab, and that Russian hackers are believed to have exploited the software to steal the classified documents.

On October 5, 2017, The Wall Street Journalreported that Russian government hackers had lifted the hacking tools from an unnamed NSA contractor who’d taken them and examined them on his home computer, which happened to have Kaspersky Antivirus installed.

On October 10, The Times reported that Israeli intelligence officers looked on in real time as Russian government hackers used Kaspersky’s antivirus network as a kind of improvised search tool to scour computers around the world for the code names of American intelligence programs.

For its part, Kaspersky has said its software detected the NSA hacking tools on a customer’s computer and sent the files to the company’s anti-malware network for analysis. In a lengthy investigation report published last month, Kaspersky said it found no evidence that the files left its network, and that the company deleted the files from its system after learning what they were.

Kaspersky also noted that the computer from which the files were taken was most likely already compromised by “unknown threat actors.” It based that conclusion on evidence indicating the user of that system installed a backdoored Microsoft Office 2013 license activation tool, and that in order to run the tool the user must have disabled his antivirus protection.

The U.S. Department of Homeland Security (DHS) issued a binding directive in September ordering all federal agencies to cease using Kaspersky software by Dec. 12.

Pho faces up to 10 years in prison. He is scheduled to be sentenced April 6, 2018.

A note to readers: This author published a story earlier in the week that examined information in the metadata of Microsoft Office documents stolen from the NSA by The Shadow Brokers and leaked online. That story identified several individuals whose names were in the metadata from those documents. After the guilty plea entered this week and described above, KrebsOnSecurity has unpublished that earlier story.